As it is generally known, wheelchairs are classified in accordance with their propulsion type, that is, manual or motorized. Motorized wheelchairs usually have higher costs of acquisition and maintenance, while manual propulsion wheelchairs require human effort to move; that is, they are propelled by manual impulsion applied either by an auxiliary person or by the user itself, who applies force onto the handrims, i.e., the circular frame attached to the external side of the rear wheels.
However, the handling and rotating movement of handrims require the moving force to be applied by the wheelchair user, who uses the front muscles of the torso and upper limbs, that is, pectoral muscles, biceps, deltoid anterior, serratus, and brachial.
The improper movement of said muscles may cause lesions and deformities in the body of the wheelchair user. The correct posture for a wheelchair user includes some rules, starting with the torso, which must be kept perpendicular, centralized, leveled, or slightly inclined forward, but preventing lateral inclinations or rotations. The legs must be in an angle of 90° to the hip, with the knees and ankles flexed to provide better stability and weight distribution. The feet must be parallel to each other. After the pelvis is stabilized, the torso must be straight and centralized, with the vertebral spine in its natural, physiological curves. The head must be straight and facing forward, supported by the neck. The upper limbs must be parallel to the torso, extended to the sides, with the elbows flexed at 90°.
Therefore, the position adopted by the wheelchair user to perform the constant movement of the wheelchair frequently causes the front abdominal muscles to be overused. This is because to move the chair forward using the handrims, the user must push them forward, causing the wheels to turn clockwise when seen by an external observer. This movement leads to an incorrect posture, as the user needs to push the torso forward and raise the elbows to produce the effort downward and forward.
This constant effort leads to a bad posture of the spine, muscle deformities, problems in the digestive system, deficiency in motor skills, lower breathing capacity, appearance of pressure ulcers, and pain that, on its turn, reflect directly in the psycho-social aspect of the wheelchair user, negatively changing its quality of life.
On the other hand, when the wheelchair user wants to move the chair backwards, the user leans on the back of the chair with the hands on the handrims, pulling them backwards, that is, pulling the wheels and turning them counterclockwise. This posture perfectly fits in the definition described above for the correct angles formed between the spine, hip, legs, and feet.